How to click really, really fast (without an Auto Clicker).
How to Get the Uncanny Clicker Achievement
The “Uncanny Clicker” Achievement is a notoriously difficult achievement for most people to obtain legitimately in Cookie Clicker. It requires the player to click the big cookie at a rate of 15 clicks per second.
Since it is not a Shadow Achievement, and therefore not considered “unfair or difficult to attain”, it does give Milk, and thus many rely on external software like Auto Clickers to obtain this.
Press Shift + Alt + Numlock to enable Mouse Keys. This will enable you to use the 5 and + keys on the numpad as click buttons, allowing you to easily obtain the achievement.